1. Field of the Invention
The present invention relates to an injection mould component for moulding the outer surface of a preform neck of a container made of plastic material, in particular a bottle. The invention also relates to a production process of said injection mould component.
2. State of the Art
An example of a bottle preform made of plastic material is illustrated in FIG. 1a. This preform, globally indicated with the numerical reference 1, comprises an elongated cylindrical portion 2, that is closed at one end, and a neck 3. The elongated cylindrical portion 2 is then stretched and blown in the stretch-blow process to form a bottle for drinks or more generally for liquids. The neck 3, provided with an open end 4, has an outer surface comprising:                a threaded end portion 5, onto which the cup-shaped cap is screwed;        a first annular flange or support ring 7, that acts as a support for transport and seal, shaped in such a way as to be able to slide on longitudinal guides that support the neck of the bottle from both sides to support and retain the bottle as it advances downstream of the container production plant;        a possible second annular flange 6, that acts as seal tearing, shaped in such a way as to retain, once the cap has been inserted into the neck 3 of the bottle, the annular seal placed at a preset position between the first flange 7 and the second flange 6;        a possible slightly conical annular portion 8, beneath the first annular flange or support ring 7, which has the function of cooperating, in the handling operations before the blowing, with said support ring 7 to slide on the longitudinal guides of advancement and transport of the bottle downstream of the container production plant.        
Where only one of the two annular flanges is provided, this flange may have the dual function of “support ring” and “seal tearing”. In this case, following coupling of the cap onto the neck 3 of the bottle, the annular seal is placed at a preset position beneath the flange at the conical annular portion 8.
In greater detail, the conical annular portion 8 is defined by the tubular stretch of preform comprised between the annular flange 7 and the joint section 9, placed between the lower end of the neck 3 and the elongated cylindrical portion 2 defining the containment body of the bottle.
The preform 1 is normally produced by means of an injection process into an injection mould 10 primarily comprising the components shown in FIG. 2. The cooling function is exercised by the respective cooling system that each of these components has.
The main components of the injection mould 10 are:                a first mould component 11, called external mould component of the neck or more simply “neck ring”, which defines the shape of the outer surface of the preform neck 3, including the threaded portion 5;        a second mould component 12, called internal mould component of the preform or more simply male component (or elongated core), which defines the inner surface of the entire preform;        a third mould component 13, called external mould component of the cylindrical portion 2 of the preform or more simply cavity, which defines the outer surface of the cylindrical portion 2.        
The first component 11 consists of two separate threaded half-inserts, the internal curved surfaces of which define, once the two half-inserts are mounted together in the rest of the mould (FIG. 2), a through opening to mould the outer surface of the preform neck 3. Each threaded half-insert is provided with a cooling circuit within its body.
The third component 13 may also, in certain cases, consist of two separate half-inserts that are cooled by means of two independent cooling circuits or by a single circuit that provides for the passage in series from one half-insert to the next.
Taking into consideration the external part of the preform neck 3, comprising the threaded portion 5, the first annular flange or support ring 7 and the conical annular portion 8 up to the level of the plane P indicated in FIG. 2, it emerges that the preform neck is cooled by the first mould component 11 and by the third mould component or cavity 13. However, the greatest weight in terms of cooling capacity is to be attributed to the first mould component 11.
It is imperative that the cooling function at the level of the preform neck is achieved in an optimal manner before extracting the preform from the mould, in order to ensure the high quality of the injected product and at the same time a contained cycle time.
Having the shortest possible cycle time in fact permits greater profitability, particularly in the mass productions that are typical of these products.
The cooling channels 14, 15 can be seen in the section of FIG. 2 in the half-inserts of the neck ring 11 and in the cavity 13 respectively. In particular, the cooling channels 14 are produced in such as way as to effectively cool only one part of the outer surface of the preform, in particular the part at the level of the support ring 7 (zone indicated by K in FIG. 1), while the zones marked with the rectangles 16, 17 in FIG. 2 (corresponding to the zones indicated by J and L of the preform in FIG. 1) are away from cooling channels and are not therefore adequately cooled.
For this reason such zones are critical from the point of view of cooling, and the moulding cycle time will depend in a determining way on the capacity of the mould to evacuate heat from said zones.
The same drawback can also be found in the case of a preform with unthreaded neck, illustrated by way of example in FIG. 1b. 
Alternative solutions to the conventional solution described above are already on the market. For example, the document EP0768164A2 describes a mould component, formed by two separate threaded half-inserts, for moulding the outer surface of a preform neck. This component partially resolves these drawbacks but has the following limitations.
Disadvantageously, the cooling channels are completely external to the upper and lower truncated cone end zones of said mould component, determining a low cooling in the corresponding zones of the preform neck. The arrangement of the two pieces of each half-insert, in fact, determines a space insufficient for the production of the channels in said truncated cone end zones by conventional processing technologies.
In addition, since the cooling channels are entirely produced by means of the normal stock-removal process, they cannot be created very close to the moulding surface and the section of these channels cannot be adequately optimised whereby they present unconnected edges that cause stagnation points of the cooling liquid and consequent low cooling in particular zones.
A further disadvantage is represented by the fact that each half-insert of said component is produced by joining two pieces by braze-welding, determining a limited structural resistance.
There is therefore a need to provide an injection mould component to mould the outer surface of the preform neck, which allows the aforementioned drawbacks to be overcome.